Continuous arcuate feed assembly

ABSTRACT

Abrasive grinding apparatus having a continuously revolving turret assembly to which a plurality of workpiece holding platens are affixed. Associated with the turret are angularly positioned stationary grinding assemblies having drum driven abrasive belts. Work enters and leaves the grinding stations at an acute angle with intermediate, complete belt coverage, whereby necessary system drive power is minimized.

This is a continuation of Ser. No. 06/495,744, filed May 18, 1983, nowabandoned.

BACKGROUND OF THE INVENTION

The present invention relates to abrasive grinding apparatus and, inparticular, to apparatus wherein the workpieces are continuously fed inan arcuate fashion and along an arcuate path so as to pass beneath thecomplete width of an orbitally driven endless abrading belt.

In the production and finishing of various metallic parts, endlessabrasive belts are oftentimes used to perform various rough and finishgrinding operations. Such apparatus produces parts at high productionspeeds with relatively accurate flat, finished dimensions and desireablesurface characteristics. Exemplary applications are in the grinding ofcast parts such as in the automobile industry for water pumps,transmissions, cylinder heads, etc. Such equipment also typicallycomprises one or more driven belts, along with associated liquid coolingand waste removal mechanisms, with such equipment being positionedrelative to the work so as to perform the various desired surfacegrinding operations.

Most typically with such apparatus, the stationary grinding assembliesare positioned such that the workpieces pass orthogonal to the directionof travel of the abrasive belt or alternatively in line with thedirection of belt travel. However, depending upon the amount of materialto be abraded from each workpiece, such arrangements for large metallicworkpieces are energy intensive and may require excessively large powerplants, particularly when single pass operation is to be achieved.

Alternatively though if the workpieces are fed to the belt at an angleand thus exposed to the abrading belt at an angle, the actual worksurface exposed at any given time is relatively small due to theaveraging effect of the angulated infeed. It is therefore a primaryobject of the present invention to take advantage of this characteristicvia a turret assembly, to which a plurality of workpiece holding platensare affixed and whereby the workpieces are rotatably passed through theapparatus where multiple operations may be accomplished, such as throughexposure to "rough" grinding and "finish" grinding abrasive operations.In this fashion, the workpieces are moved continuously through theapparatus and exposed to the abrading belts at an angle which requiresless overall system power than would otherwise be required.

Rotational or arcuately driven feed assemblies for various grindingapparatus have been employed previously, as for example in U.S. Pat.Nos. 2,406,728 and 2,855,730. The apparatus disclosed in each of thesepatents, however, is distinguishable from the present apparatus. Inparticular, which the U.S. Pat. No. 2,406,728 has an arcuate infeedassembly, it follows the common practice of presenting the workpiece inan orthogonal fashion to the abrading belt. U.S. Pat. No. 2,855,730 onthe other hand, presents the workpiece in an angular fashion; however,it is distinguishable from the apparatus of the present invention in itsstructure and application.

The above objects, advantages and distinctions of the present apparatusas well as others will however, become more apparent upon a reading ofthe following description with respect to the following drawings.

SUMMARY OF THE INVENTION

A continious feed endless belt abrading system having an arcuate feedassembly supporting a plurality of platens to which desired workpiecesare attached for exposure to one or more grinding operations. Loadingand unloading of the workpieces may be accomplished either manually orthrough automatic equipment. Portioned about and apart from one anotherand relative to the feed assembly are a pair of workpiece-abradingstations, each station comprising a resiliently biased adjustableendless belt abrading mechanisms disposed relative to the path of theworkpieces such that the workpieces are introduced into and exposed tothe abrading surfaces of the belts at an angle relative to the beltmotion. This arrangement has been found to significantly reduce systempower requirements.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagramatic perspective view in partial cut-away of theabrasive grinding apparatus of the present invention, with the beltdrive and control systems being removed from the assemblies;

FIG. 2 is a top view of the apparatus illustrated in FIG. 1, and showingthe normal positioning of the grinding heads relative to the rotatinginfeed assembly;

FIG. 3 is a side view, partially broken away, of a typical grindingassembly for use in the apparatus of FIGS. 1 and 2; and

FIG. 4 is a front view, partially broken away, of the grinding assemblyillustrated in FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, a generalized perspective view is shown of thepresent apparatus and the relative positioning of its primarycomponents. In this regards, the apparatus is generally comprised of acabinet 2 which contains a "rough" endless belt grinding assembly 4 anda "finish" endless belt grinding assembly 6. Each grinding assemblycomprises a driven lower contact drum 8, an upper idler drum 10 and anabrading belt 12. The belts 12 typically have an abrasive grit selectedfor the material of construction of the work and the nature of theoperation, such as a coarse grit for rough work and a finer abrasivegrit for finish work. Each belt also typically is 5 to 50 inches widesufficiently to handle the operation selected. The grinding assemblies 4and 6 are, in turn, driven via associated drive motors (not shown) whichare positioned on the respective right and left sides of the cabinet 2and which are coupled to the grinding assemblies 4 and 6 via associateddrive pulleys and belt mechanisms.

Positioned beneath the grinding assemblies 4 and 6 is a work piecesupporting turret assembly 16 which revolves about a center axis 18 viaan appropriate drive mechanism and motor (not shown). Attached to thetable 20 of the assembly 16 are a plurality of platens 22 of variousdesired shapes and sizes and having various indexing holes and pegsformed therein for subsequent alignment with various types of workpieces that will be mounted thereto such turret assemblies are known inthe art.

Thus, upon mounting the workpieces to the platens at an infeed station,the platens are revolved so as to bring the workpieces first beneath therough grinding assembly 4 and then beneath the finish grinding assembly6, after which the workpiece is removed at the outfeed station. Itshould be noted too that a coolant (typically water) is supplied to thedrums of the individual grinding assemblies 4 and 6 via a coolant inletport continued on the back of the cabinet 2 and sprayed on the workpieces during normal operation so as to cool the abrasive belts 12 andworkpieces. Also and not shown, the cabinet 2 contains associated wasteremoval apparatus for collecting the waste water and material abrasivelyremoved from the workpieces so as not to unduly contaminate the grindingoperations of subsequently treated workpieces. It is should also benoted that typically spaced about the periphery of the table 20 aremounted a number of safety switches (not shown) for detecting positions,including the elevation and radial positions of the workpieces as wellas a part gauge for detecting the extent of abrasive belt wear.

Referring next to FIG. 2, a generalized top view is shown of theapparatus and the relative positioning of the grinding assemblies 4 and6 with respect to the rotating turret 16. From this figure, the grindingassembly drive motors 24 and associated V-belt drive pulleys 26 andV-belts 28 can more readily be seen. More particularly though, it is tobe recognized that as the workpiece containing platens 22 move on theirarcuate paths along with turret table 20, they initially meet and passunder the abrading belts 12 at an acute angle, which angle graduallychanges as the work is rotated through its path and exposed to thesurface of the belt. Thus, the work enters along the bias relative tothe path or axis of the abrasive belt 12 so as to incrementally exposemore and more surface area of the workpiece to the belt as the workpasses thereunder. For the present embodiment, it has been determinedthat when abrading approximately 0.100 inches from aluminum or ironcastings of approximately 60 square inches, an initial acute angle of 15degrees to 60 degrees is preferred in that the horsepower requirementsof the drive motors 24 can be reduced from about 65 horsepower to about50 horsepower. Such a power reduction is further significant in thatsignificant costs are saved not only from the initial purchase, but alsoover a span of time, due to the reduced power demands.

Referring next to FIG. 3, a partially cut-away and sectioned end view isshown of a typical grinding head assembly, such as illustrated at 4 and6 in FIG. 1, with this figure illustrating the detail of the adjustingmechanism utilized in the head assembly. In addition to the contact drum8 and idler drum 10, each assembly is comprised of an intermediateextendable air cylinder 34 used to properly tension the endless abrasivebelt.

With continuing reference to FIG. 3, and also with reference to FIG. 4,the contact drum 8 may be adjusted either upwardly or downwardly inrelative position from the center bar 48 via two screw-jacks 40, withdrum 8 being laterally guided via four individual guide posts (notshown). The screw-jacks 40 operate concurrently, or cooperatively viacouplings 46 and jack-shaft 42 and 44.

Normally, controlled adjustment of contact drum 8 is required in orderto change and/or establish the grinding plane of that head independentlyof the grinding plane of the other grinding heads of the overallapparatus. For example, the first grinding head is normally set with itsgrinding plane contacting the work to establish a rough dimension, withthe grinding plane of the second grinding head being established toremove a modest amount of additional material to provide the work with afinished part dimension. In the embodiments illustrated in FIGS. 1 and2, the first grinding head is included in assembly generally designated4, with the finish grinding being accomplished by the grinding headincluded in assembly generally designated 6.

Air bladders are included in the adjustment system, with such bladdersbeing shown at 30--30. These air bladders function as a machine overloadprotection device. The force created by the air bladders hold the drumguide and assembly in place against a positive stop. This arrangementprovides a means for holding the contact drum 8 on or along thepre-established or desired grinding plane.

In FIG. 3, the positive stop is illustrated at 49, which is the ledge orlower-most surface of the groove 49A formed in center bar 48. Plate 51,which is coupled to the open-end edges of inverted channel 53 forms abox-like support frame for applying normal grinding force to thegrinding head, while at the same time providing overload protection inthe event of an overly thick or mis-fixtured part passing under thedrum. In such an event, the box-arrangement consisting of plate 51 andchannel 53 will raise upwardly off of stop surface 49, thus achievingoverload protection for the machine. It may be seen, therefore, that airbladder 30 is provided to hold the entire adjusting unit downwardlyagainst stop 49.

The vertical adjustment for establishing the grinding plane for drum 8is obtained with adjustable screw-jacks 40--40. Thus, jacks 40 alongwith guide posts 41--41 which are coupled thereto by means of plate 43are utilized to establish the vertical elevation or disposition of drum8.

When a plurality of screw-jacks such as screw-jacks 40 are utilized, itmay be desirable to gang the jack shafts together, such as jack shafts42 and links 46 so as to achieve equal motion on the individual jackshafts. Such an arrangement expedites change-over, as well as providinga means for maintaining control of the grinding plane. It should also benoted that an appropriate bracket 52 supports the bearings 54 and axleshaft 56 of the lower contact drum. Similarly, an axle 58 and bearings60 rotatably support the idler drum 10.

The air pressure maintained in bladders 30 is regulated and maintainedremotely. The force created by the bladders 30--30 determines theavailable grinding force. Should an excessive grinding pressure beencountered, the bladder will accomplish relief by permitting contactdrum 8 to rise, thereby preventing over-stress or overload conditionsfrom occurring on the machine.

The brake 38 is provided for use in emergency situations, and achievesemergency stops when appropriate. Brake 38 is activated by the machineoperator pushing or energizing the emergency stop button, orautomatically in the event the abrasive belt should sever or move toofar out of its normal operating path. In the event of a fracture of theabrasive belt, idler drum 10 would normally continue to rotate for anextended period of time due to inertia forces alone. In order to reducethe time required for installation of a fresh abrasive belt, brake 38 isenergized automatically when the system senses that an abrasive belt hasruptured, separated, or broken, or is not found in its normal operatingpath or position.

With attention being briefly directed to FIG. 2 of the drawings, bracket32 is an outboard support bracket used to stabilize the grinding headwhile grinding is occurring, and to prevent the grinding head fromdeflecting upwardly and laterally in response to forces created by thenormal resistance to the grinding load. This support may be defined as aswing support, and is normally hingedly secured, as indicated, to permitthe support to be removably positioned to permit abrasive belt loading.

In operation, power is applied to the lower contact drum 8 and axleshaft 56 via the associated drive motor 24 and the pulley sheave 26attached fast on axle shaft 56. Thus, as the contact drum 8 rotates itcauses the abrasive belt 12 to remove the desired thickness of materialfrom the workpiece. A self-center tracking assembly 64 associated withthe idler drum 10, also permits the apparatus to electronically monitorthe belt position relative to the drums 8 and 10 so that it remainscentered. Electrical belt-tracking systems are commercially available.

While the present invention has been described with respect to itsvarious preferred components and configuration, it is to be recognizedthat various modifications may be made without departing from the scopeof the presently described invention. It is therefore contemplated thatthe following claims should be interpreted in conjunction with thepresent description to include all such equivalent structures.

What is claimed is:
 1. An endless abrasive belt grinding assemblycomprising:(a) first and second driven endless abrasive belt grinders,wherein each grinder comprises:(1) frame means; (2) a lower drivencontact drum and an upper idler drum operatively retained within saidframe means to form a working drum pair and with said contact drum beingadapted for rotatable motion about the central axis thereof; (3) anendless abrasive belt having a longitudinal axis and being wrapped abouteach said working drum pair and arranged for travel along the directionof said longitudinal axis, with said longitudinal belt axis beinggenerally normal to the central axis of the lower contact drum of saidworking drum pair; (4) screw-jack means coupled to said frame means anddisposed intermediate said contact drum and said idler drum foradjustably positioning said contact drum to establish the grinding planeof said abrasive belt; and (5) air-filled bladder means operatively andresiliently coupling said contact drum to said frame means for applyinga substantially continuous bias force against said contact drum as itengages workpieces passing along said grinding plane thereunder; (6) acircular rotating table having a centrally disposed axis of rotation,means for rotating said table at a substantially continuous arcuate rateof speed, and with a plurality of work-retaining platens thereon, eachplaten being disposed on said rotating table in radially spacedrelationship to said axis of rotation and being arranged to move along aclosed circular path at said substantially continuous rate of speed, andsaid work-retaining platens being further adapted to receive and supportat least one workpiece thereon for arcuately conveying said workpiece onsaid rotating table along said circular path and immediately beneath thecontact roll of each of said working drum pairs within said grindingassemblies to create a working line of contact between said abrasivebelt and the surface of said workpiece and thereby remove a desiredamount of material from the thickness of said workpiece; and (7) thecentral axis of rotation of the lower contact drum of each working drumpair being disposed and positioned relative to the surface of saidrotating table and to the arcuately moving workpieces secured theretosuch that the angular relationship between the contact drum central axisof rotation and the direction of motion of the work-retaining platen atthe point where said work retaining platen moves directly beneath saidcentral axis of rotation and along said closed circular path ranges frombetween about 15 degrees and 60 degrees.